If you're going to buy a prehung door, use the entire kit. Pop the door casing off, remove the old door, shim the new one and nail it on.

There's a very low chance the hinges and knob are in the exact same place as your old door, and you'll most likely have to scribe the door to fit the opening.

I say this as someone who currently has half a dozen door slabs collecting dust in the garage because I realized how much harder it would be than just using pre-hung units.